Born from the separation of a fragment of Gondwana 80 million years ago, Grande-Terre - the main island of New Caledonia - emerged about 45 million years ago, after a period of oceanic immersion. This uplift process, followed by the sliding of part of the oceanic plate and by erosion, led to the establishment of a metamorphic crust rich in minerals over about a third of the total surface of Grande-Terre including these laterite massifs from the region of Poro.